The present invention relates to very fine denier polyester yarn made from poly(trimethylene terephthalate) fibers.
Polyester yarns having very fine denier are highly desirable for manufacturing fabrics used in the garment industry. Such yarns are desirable because they yield a light-weight material having excellent properties such as softness. The softness of a yarn and fabric is a measure of how soft a material feels to the touch. A yarn and fabric used for many clothing apparel items require a high degree of softness.
Very fine denier polyester fibers currently known in the art are made using polyethylene terephthalate. Such yarns provide softness suitable for many garments such as, e.g., dresses, jackets and other ladies"" apparel. However, because polyethylene terephthalate has a high Young""s modulus, the maximum softness achieved is not suitable for garments requiring ultra-soft touch.
There is therefore a need in the art for very fine denier polyester yarns having superior softness quality. Theoretically, polyester yarns made from a polymer having a low Young""s modulus should yield the desirable properties. However, attempts to commercially manufacture such a fine denier polyester yarn from poly(trimethylene terephthalate) have not been successful due to various manufacturing problems. For example, when attempting to make very fine denier yarns from poly(trimethylene terephthalate), excessive breaks in the fibers have been experienced. Further, it was thought in the prior art that the tenacity of poly(trimethylene terephthalate) was too low to successfully make a very fine denier yarn.
The present invention comprises a drawn yarn made from a partially oriented feed yarn, said feed yarn made from a polyester polymer melt-extruded at a spinning temperature between about 255xc2x0 C. and 275xc2x0 C., wherein said polymer comprises at least 85 mole % poly(trimethylene terephthalate) wherein at least 85 mole % of repeating units consist of trimethylene units, and wherein said polymer has an intrinsic viscosity of at least 0.80 dl/g, and wherein said drawn yarn has the following characteristics:
(a) a denier per filament less than about 1.5; and
(b) an actual draw ratio within 10 percent of a predicted draw ratio, wherein the predicted draw ratio is determined according to: [(elongation to break of the feed yarn)+115]/[(elongation to break of the drawn yarn)+115)].
The present invention further comprises a process for making a drawn yarn from a partially oriented feed yarn, comprising the steps:
(a) extruding a molten polyester polymer at a temperature between about 255xc2x0 C. and about 275xc2x0 C. through a spinneret to form filaments, wherein said polymer comprises at least 85 mole % poly(trimethylene terephthalate) wherein at least 85 mole % of repeating units consist of trimethylene units, and wherein said polymer has an intrinsic viscosity of at least 0.80 dl/g;
(b) cooling the filaments by exposing them to a flow of quench air;
(c) coating the filaments with a spin finish;
(d) heating the filaments to a temperature greater than the glass transition temperature of the filaments, but less than 200xc2x0 C., prior to drawing the filaments; and
(e) drawing the filaments between a set of feed rolls to produce a denier per filament less than about 1.5 and an actual draw ratio within 10 percent of a predicted draw ratio, wherein the predicted draw ratio is determined according to: [(elongation to break of the feed yarn)+115]/[(elongation to break of the drawn yarn)+115)].
The present inventions further comprises a fine denier feed yarn made from a polyester polymer melt-extruded at a spinning temperature between about 255xc2x0 C. and about 275xc2x0 C., wherein said polymer comprises at least 85 mole % poly(trimethylene terephthalate) wherein at least 85 mole % of repeating units consist of trimethylene units, and wherein said polymer has an intrinsic viscosity of at least 0.80 dl/g, and wherein said fine denier feed yarn has a denier per filament less than about 2.